Anti-obesity stent

ABSTRACT

The anti-obesity stent includes a tubular structure having outer and inner surfaces and proximal and distal ends. The tubular structure is sized to fit within a duodenum in substantially coaxial relation therewith. The tubular structure is impervious or semi-permeable to digestive substances and chyme within the duodenum. The anti-obesity stent includes a transport structure at least a part of which is coincident with or connected to the outer surface. The transport structure extends to the distal end of the tubular structure. At least one retainer structure is connected to the tubular structure. The retainer structure secures the tubular structure within the duodenum such that the transport structure is positioned to receive digestive fluids from a papilla of Vater on an inner surface of the duodenum. The transport structure provides a conduit for the digestive fluids therein to flow to the distal end.

FIELD OF THE INVENTION

The present invention relates generally to anti-obesity stents andmethods for using the same, and more specifically, to anti-obesitystents which are secured in the duodenum adjacent to the stomach toreduce digestion and absorption of food.

BACKGROUND OF THE INVENTION

The incidence of obesity and its associated health-related problems hasbecome significant. The causes of obesity may involve a complexinterplay of genetic, environmental, psycho-behavioral, endocrine,metabolic, cultural, and socio-economic factors. Severe obesity isfrequently associated with significant comorbid medical conditions,including coronary artery disease, hypertension, type II diabetesmellitus, gallstones, nonalcoholic steatohepatitis, pulmonaryhypertension, and sleep apnea. Obesity is a leading cause of preventabledeath in the U.S. The spectrum of comorbid conditions associated withobesity includes cancer, osteoarthritis, and heart disease. The economiccost of obesity is substantial.

Current treatments for obesity range from diet, exercise, behavioralmodification, and pharmacotherapy to various types of surgery, withvarying risks and efficacy. In general, nonsurgical treatments, althoughless invasive, achieve only relatively short-term and limited weightloss in most patients. Non-surgical treatments are utilized for patientssuch as with a body-mass index (BMI) which is greater than 30, and havenot proven very effective. Surgical treatments include gastroplasty torestrict the capacity of the stomach to hold large amounts of food, suchas by stapling or “gastric banding”. Other surgical procedures includegastric bypass and gastric “balloons” which, when deflated, may beinserted into the stomach and then are distended by filling with salinesolution.

Surgical interventions may be performed on those patients with a BMIwhich is greater than 40 (deemed morbidly obese). Surgical interventionsmay include restrictive operations that reduce the size of the stomachpouch to limit food intake. Surgical interventions may also includemalabsorptive procedures that rearrange the small intestine in anattempt to decrease the functional length or efficiency of nutrientabsorption, or a combination thereof. One combination procedure isGastric Bypass (GPB or Roux-en-Y) which has been effective for mostpatients who maintain about 70% of excess weight loss after 5 years, and50% thereof after 10 years. Both of these types of procedures may beperformed laparoscopically, but may have complications. Also, GPB isnormally irreversible. Other treatment approaches are being considered.Excess weight loss is the loss of weight which is greater than the idealbody weight.

The need exists for low cost, less invasive interventions for thetreatment of obesity, including morbid obesity.

SUMMARY OF THE INVENTION

The anti-obesity stent of the present invention includes a tubularstructure having outer and inner surfaces and proximal and distal ends.The tubular structure is sized to fit within a duodenum in substantiallycoaxial relation therewith. The tubular structure is impervious orsemi-permeable to digestive substances and chyme within the duodenum.Chyme is the partially digested food which flows into the duodenum fromthe stomach. The anti-obesity stent includes a transport structure atleast a part of which is coincident with or connected to the outersurface. The transport structure extends to the distal end of thetubular structure. At least one retainer structure is connected to thetubular structure. The retainer structure secures the tubular structurewithin the duodenum such that the transport structure is positioned toreceive digestive fluids from a papilla of Vater on an inner surface ofthe duodenum. The transport structure provides a conduit for thedigestive fluids therein to flow to the distal end.

The anti-obesity stent, when secured in the proper location within theduodenum, reduces or prevents mixing of the chyme and digestivesubstances within the duodenum. The digestive substances within theduodenum include digestive fluids, such as biliary and pancreaticjuices, which reach the interior of the duodenum by flowing through thepapilla of Vater which is contiguous with the inner surface of theduodenum. The digestive fluids are supplied to the papilla of Vater bythe bile and pancreatic ducts. The anti-obesity stent reduces orprevents mixing of the chyme and digestive fluids by reducing orpreventing the digestive fluids which flow through the papilla of Vaterfrom passing through the tubular structure. Consequently, mixing of thedigestive fluids with the chyme in the region of the duodenum which isoccupied by the anti-obesity stent is reduced or prevented. This reducesthe exposure of the chyme to the digestive fluids which reduces theassociated chemical breakdown thereof. This is a result of the tubularstructure being semi-permeable or impervious to the chyme. The reductionin the mixing of the chyme and digestive fluids provided by theanti-obesity stent reduces the caloric intake by the patient. Also, thisreduction in the mixing reduces the breakdown of fats because the bileis separated from the chyme over the axial length of the anti-obesitystent. Consequently, the chemical transformation of the chyme by thedigestive fluids which is normally required for absorption of thenutrients, fats and other substances in the chyme by the duodenum isreduced.

The anti-obesity stent reduces the absorption of fats by the smallintestine, which includes the duodenum, by the following mechanisms: (i)the anti-obesity stent separates the chyme from the bile which issecreted by the papilla of Vater over the axial length of the stent;(ii) the anti-obesity stent separates the chyme from the absorptivesurfaces of the small intestine which reduces the absorption of thenutrients, fats and other substances in the chyme by the smallintestine; and (iii) the bile which is located between the anti-obesitystent and the absorptive surfaces of the small intestine is reabsorbedby the absorptive surface over the axial length of the stent whichfurther reduces the availability of the bile exiting at the distal endof the stent to breakdown fats in the chyme.

The reduction in the mixing of the chyme and bile, and the separation ofthe chyme from the absorptive surfaces of the duodenum provided by theanti-obesity stent may significantly reduce the breakdown and absorptionof fat in the chyme. Such a significant reduction may result from theabsorption of fat possibly being required in the duodenum to beeffective.

Additionally, the anti-obesity stent reduces the absorption of thenutrients, fats and other substances in the chyme by the duodenum. Thisreduced absorption results from the tubular structure beingsemi-permeable or impervious to the chyme. As a result, the chyme whichis contained within the tubular structure is partially or completelyprevented from reaching the inner surface of the portion of the duodenumin which the anti-obesity stent is located. Consequently, the portion ofthe duodenum in which the anti-obesity stent is located is partially orcompletely prevented from absorbing the nutrients, fats and othersubstances in the chyme. Reducing the absorption of the nutrients, fatsand other substances by the duodenum reduces the caloric intake by thepatient. Also, reducing the absorption of the nutrients, fats and othersubstances reduces the fat intake by the patient which typically reducesthe weight thereof.

The anti-obesity stent does not obstruct the passage and flow of thedigestive fluids through the papilla of Vater. This allows flow of thedigestive fluids through the papilla of Vater into the anti-obesitystent. The anti-obesity stent further provides for the digestive fluidsto be conveyed through the transport structure to the distal end of thetubular structure. The passage or flow of the digestive fluids throughthe papilla of Vater which is not obstructed by the anti-obesity stentis beneficial because obstruction of such passage or flow through thepapilla of Vater may be undesireable.

The anti-obesity stent separates the food and chyme, which flows fromthe stomach into the duodenum, from the digestive fluids which includebile acids and pancreatic enzymes and which promote lipid absorption.This separation by the anti-obesity stent is provided at the locationthereof in the duodenum which is the beginning of the small intestine.The anti-obesity stent treats obesity using a mal-absorptive method.Separating the food from the digestive fluids may reduce the amount ofdigestion and, consequently, the amount of weight a person gains fromeating a specific quantity of food. Also, such separation reduces theabsorption of the nutrients, fats and other substances in the chyme.

These and other features of the invention will be more fully understoodfrom the following description of specific embodiments of the inventiontaken together with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is an anatomical elevational view of a stomach, duodenum andadjacent portions of the alimentary canal, the wall of the pyloricportion of the stomach and duodenum being broken away to show ananti-obesity stent in accordance with the present invention;

FIG. 2 is an enlarged view of the pyloric portion of the stomach andduodenum in which portions thereof are broken away to show theanti-obesity stent of FIG. 1, the anti-obesity stent being shown ashaving a substantially straight tubular structure and a transportstructure which includes circumferential and axial grooves;

FIG. 3 is a perspective view of the anti-obesity stent of FIG. 2;

FIG. 4 is a perspective view of an alternative embodiment of theanti-obesity stent of FIG. 1, the anti-obesity stent being shown ashaving a substantially straight tubular structure and an alternativetransport structure;

FIG. 5 is a perspective view of a further alternative embodiment of theanti-obesity stent of FIG. 1, the anti-obesity stent being shown ashaving a substantially straight tubular structure and a furtheralternative transport structure;

FIG. 6 is a longitudinal cross-sectional view of a further alternativeembodiment of the anti-obesity stent of FIG. 1, the anti-obesity stentbeing shown as having a substantially straight tubular structure whichincludes proximal and distal portions, the anti-obesity stent beingfurther shown as having a further alternative transport structure;

FIG. 7 is a perspective view of a further alternative embodiment of theanti-obesity stent of FIG. 1, the anti-obesity stent being shown ashaving a substantially straight tubular structure and a furtheralternative transport structure;

FIG. 8 is a perspective view of a further alternative embodiment of theanti-obesity stent of FIG. 1, the anti-obesity stent being shown ashaving a substantially straight tubular structure and a furtheralternative transport structure;

FIG. 9 is a perspective view of a further alternative embodiment of theanti-obesity stent of FIG. 1, the anti-obesity stent being shown ashaving a substantially straight tubular structure which is distal of thepapilla of Vater;

FIG. 10 is a longitudinal cross-sectional view of a further alternativeembodiment of the anti-obesity stent of FIG. 1, the anti-obesity stentbeing shown as having a substantially straight tubular structure and aproximal portion which is outwardly flared;

FIG. 11 is a longitudinal cross-sectional view of a further alternativeembodiment of the anti-obesity stent of FIG. 1, the anti-obesity stentbeing shown as having a substantially straight tubular structure andproximal and distal anchors; and

FIG. 12 is a perspective view of a further alternative embodiment of theanti-obesity stent of FIG. 1, the anti-obesity stent being shown ashaving a substantially straight tubular structure and a furtheralternative transport structure.

Corresponding reference characters indicate corresponding partsthroughout the several views of the drawings.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawings and more particularly to FIG. 1, a centralportion of the alimentary canal 10 in which the anti-obesity stent 12 islocated is illustrated. This portion of the alimentary canal 10 includesthe distal segment of the esophagus 15, the stomach 17, and the duodenum20. The duodenum 20 is the proximate segment of the small intestine. Thestomach 17 has a pyloric portion 22 which leads to the duodenum 20 byway of the gastric outlet or pylorus 25. The pylorus 25 forms the distalaperture of the stomach 17 and has an enclosing circular layer of musclewhich is normally contracted to close the aperture but which relaxes toprovide an open but restrictive passage. Although subject to substantialvariation in different individuals, the pylorus 25 has a maximum opendiameter of about 2 cm and the duodenum 20 has a diameter whichtypically is about 18 to 20 mm in a representative patient. The chyme 26passes from the pyloric portion 22 through the pylorus 25 into theduodenum 20. The duodenum 20 has an inner surface 27 and a papilla ofVater 30 which is a trumpet-mouthed dilatation of the duodenal wall atthe opening of the fused bile and pancreatic ducts. Digestivesubstances, which include digestive fluids 31, are supplied through thepapilla of Vater 30, and flow into the interior of the duodenum 20.

The anti-obesity stent 12 is located within the duodenum 20 as shown inFIG. 1. As shown in FIG. 2, the anti-obesity stent 12 includes a tubularstructure 32 which has outer and inner surfaces 35, 37. The tubularstructure 32 has proximal and distal ends 40, 42 and is sized to fitwithin the duodenum 20 in substantially coaxial relation therewith.Preferably, the axial positioning of the tubular structure 32 providesfor the distal end 42 to extend to the ligament of Treitz or to an axialposition which is distal thereof. The tubular structure 32 typically hasan annular cross section. Alternative embodiments of the anti-obesitystent 12 are possible in which the tubular structure 32 has anon-annular cross section, such as elliptical. The tubular structure 32includes embodiments which extend from the duodenum 20 through thepylorus 25. Such embodiments of the tubular structure 32 may have asafety factor such that the section thereof which extends through thepylorus 25 has an outer diameter which is substantially larger than theopening of the pylorus. Such a safety factor provides for the tubularstructure 32 to be retained in the pylorus 25. The tubular structure 32is impervious or semi-permeable to digestive substances and chyme 26within the duodenum 20 which partially or completely prevents the chymewithin the tubular structure from contacting the inner surface 27 of theduodenum 20 to partially or completely prevent absorption of thenutrients, fats and other substances in the chyme by the portion of theduodenum in which the anti-obesity stent 12 is located. Alternativeembodiments of the anti-obesity stent 12 are possible in which thetubular structure 32 is located in sections of the intestine which areaxially displaced relative to the duodenum 20. Further alternativegastro-intestinal applications of the anti-obesity stent 12 arepossible.

The tubular structure 32 may be formed of expandedpolytetrafluoroethylene (ePTFE) or polyurethane. The tubular structure32 may be formed of biocompatible materials, such as biocompatiblepolymers including those which are known. Such polymers may includefillers such as metals, carbon fibers, glass fibers or ceramics. Also,such polymers may include olefin polymers, polyethylene, polypropylene,polyvinyl chloride, polytetrafluoroethylene which is not expanded,fluorinated ethylene propylene copolymer, polyvinyl acetate,polystyrene, poly(ethylene terephthalate), naphthalene dicarboxylatederivatives, such as polyethylene naphthalate, polybutylene naphthalate,polytrimethylene naphthalate and trimethylenediol naphthalate,polyurethane, polyurea, silicone rubbers, polyamides, polycarbonates,polyaldehydes, natural rubbers, polyester copolymers, styrene-butadienecopolymers, polyethers, such as fully or partially halogenatedpolyethers, copolymers, and combinations thereof. Also, polyesters,including polyethylene terephthalate (PET) polyesters, polypropylenes,polyethylenes, polyurethanes, polyolefins, polyvinyls,polymethylacetates, polyamides, naphthalane dicarboxylene derivatives,and natural silk may be included in the tubular structure 32. Inalternative embodiments, the tubular structure 32 may be a polymersleeve.

The tubular structure 32 may be incorporated in a composite structurewhich also includes a stent structure. The stent structure may includeelongate members, such as wires, or a tubular structure having cutouts.The stent structure may be connected to the tubular structure 32 by aseal. The tubular structure 32 may be located within the stent structurein coaxial relation therewith. Such a tubular structure 32 which iswithin the stent structure may be connected thereto such that thetubular structure is in hanging relation to the stent structure. Theconnection of the tubular structure 32 to the stent structure may beprovided by one or more threads, filaments or similar connectors.

A preferred embodiment of such a tubular structure 32 within a stentstructure includes the tubular structure having a diameter which issubstantially the same as the diameter of the stent structure. Such apreferred embodiment further includes the end of the tubular structure32 through which the fluid enters therein being connected to thecorresponding end of the stent structure. These ends of the tubularstructure 32 and stent structure are typically referred to as theproximal ends. Connection of the proximal ends of the tubular structure32 and stent structure substantially eliminates any radial clearancebetween the proximal ends. Such a radial clearance may provide a pathfor the fluid flow to bypass the lumen of the tubular structure 32.Additional connections of the tubular structure 32 to the stentstructure at axial locations which have a distal relation to theproximal ends may be provided.

The connections of the tubular structure 32 to the stent structurewithin which the tubular structure is located limit radially inwarddisplacement thereof. The outer location of the stent structure relativeto the tubular structure 32 limits radially outward displacementthereof.

In a further alternative embodiment, the tubular structure 32 may belocated within an outer stent structure and an inner stent structure maybe located within the tubular structure 32. Outward radial displacementof the tubular structure 32 is limited by the outer stent structure.Inward radial displacement is limited by the inner stent structure. Theconnection between the tubular structure 32 and one or more stentstructures which are within one another in coaxial relation may providefor the adjacent outer and inner surfaces to be contiguous with oneanother. Alternatively, the connection may provide for a transverse orradial clearance between the tubular structure 32 and one or more stentstructures.

The tubular structure 32 may be a sleeve structure within which islocated a stent structure. The sleeve structure 32 may be a PERMALUME®silicone covering for a stent structure constituted by a WALLSTENT® RXBiliary Endoprosthesis, which are made by the Boston ScientificCorporation.

The tubular structure 32 may be a stent structure, such as a WALLSTENT®RX Biliary Endoprosthesis made by the Boston Scientific Corporation.Alternatively, the stent structure may be a NIR® Biliary Stent Systemmade by the Boston Scientific Corporation. Further alternative stentstructures are possible.

The stent structure of the tubular structure 32 may be formed ofmaterials such as nitinol, Elgiloy, stainless steel, cobalt chromium,including MP35N, cobalt-based alloy, tantalum, niobium, platinum, gold,titanium, combinations thereof and other biocompatible metals, polymersand materials. Additionally, the stent structure may include structuralmembers which have an inner core formed of tantalum, gold, platinum,iridium, or a combination thereof, and an outer cladding of nitinol toprovide composite members for improved radio-opacity or visibility.Examples of such composite members are disclosed in U.S. PatentApplication Publication No. 2002/0035396 which is hereby incorporated byreference herein.

The stent structure of the tubular structure 32 may have variousembodiments. For example, the stent structure may be self-expanding orexpandable by a balloon. The stent structure may include one or morecoiled stainless steel springs, helically wound coil springs including aheat-sensitive material, or expanding stainless steel stents formed ofstainless steel wire in a zig-zag pattern. The stent structure may becapable of radially contracting or expanding, such as by radial orcircumferential distension or deformation. Self-expanding stentstructures include stent structures which mechanically urge the stentstructure to radially expand, and stent structures which expand at oneor more specific temperatures as a result of the memory properties ofthe stent material for a specific configuration. Nitinol is a materialwhich may be included in the stent structure for providing radialexpansion thereof both by mechanical urging, or by the memory propertiesof the nitinol based on one or more specific temperatures. The stentstructure may include one or more of the stent structures disclosed inU.S. Pat. Nos. 4,503,569, 4,733,665, 4,856,516, 4,580,568, 4,732,152,and 4,886,062 which are hereby incorporated by reference herein.

The tubular structure 32 may be treated with anti-thrombogenic agents(such as heparin, heparin derivatives, urokinase, and PPack(dextrophenylalanine proline arginine chloromethylketone)),anti-proliferative agents (such as enoxaprin, angiopeptin, or monoclonalantibodies capable of blocking smooth muscle cell proliferation,hirudin, and acetylsalicylic acid), anti-inflammatory agents (such asdexamethasone, prednisolone, corticosterone, budesonide, estrogen,sulfasalazine, and mesalamine),antineoplastic/antiproliferative/anti-miotic agents (such as paclitaxel,5-fluorouracil, cisplatin, vinblastine, vincristine, epothilones,endostatin, angiostatin and thymidine kinase inhibitors), anestheticagents (such as lidocaine, bupivacaine, and ropivacaine),anti-coagulants (such as D-Phe-Pro-Arg chloromethyl keton, an RGDpeptide-containing compound, heparin, antithrombin compounds, plateletreceptor antagonists, anti-thrombin antibodies, anti-platelet receptorantibodies, aspirin, prostaglandin inhibitors, platelet inhibitors andtick antiplatelet peptides), vascular cell growth promotors (such asgrowth factor inhibitors, growth factor receptor antagonists,transcriptional activators, and translational promotors), vascular cellgrowth inhibitors (such as growth factor inhibitors, growth factorreceptor antagonists, transcriptional repressors, translationalrepressors, replication inhibitors, inhibitory antibodies, antibodiesdirected against growth factors, bifunctional molecules consisting of agrowth factor and a cytotoxin, bifunctional molecules consisting of anantibody and a cytotoxin), cholesterol-lowering agents, vasodilatingagents, and agents which interfere with endogenous vascoactivemechanisms.

The anti-obesity stent 12 has a transport structure 45 at least a partof which is coincident with or connected to the outer surface 35 of thetubular structure 32. One embodiment of the transport structure 45,illustrated in FIGS. 2 and 3, includes a circumferential groove 47 whichis formed on the outer surface 35 of the tubular structure 32. Thecircumferential groove 47 is continuous and transverse relative to thetubular structure 32. The circumferential groove 47 is circular as aresult of the tubular structure 32 having an annular cross section, asshown in FIG. 3. The portions of the outer surface 35 which arecontiguous with the circumferential groove 47 have respective outerdiameters which are greater than the diameter of the inner surface 27 ofthe duodenum 20 to provide a seal between these portions of the outersurface 35 and the inner surface 27 when the anti-obesity stent 12 islocated within the duodenum 20. Such a seal prevents leakage of thedigestive fluids 31 within the circumferential groove 47 between theinner and outer surfaces 27, 35.

The portions of the outer surface 35 which are contiguous with thetransverse groove 47 have corresponding diameters as a result of thetubular structure 32 having an annular cross section. Alternativeembodiments of the tubular structure 32 are possible which havenon-annular cross sections.

The transport structure 45, illustrated in FIGS. 2 and 3, includes anelongate axial groove 55 which is formed on the outer surface 35 of thetubular structure 32. The axial groove 55 has an axial orientationrelative to the tubular structure 32 and communicates with thecircumferential groove 47. The axial groove 55 provides a conduit forthe digestive fluids 31 in the circumferential groove 47 to be conveyedto the distal end 42.

The anti-obesity stent 12 has at least one retainer structure 50 whichis connected to the outer surface 35 of the tubular structure 32. Theretainer structure 50 secures the tubular structure 32 within theduodenum 20 such that the axial position of the circumferential groove47 is substantially the same as the axial position of the papilla ofVater 30 relative to the duodenum. One embodiment of the retainerstructure 50 is the diameter of the outer surface 35 of the tubularstructure 32 being sufficiently large to press against the inner surface27 of the duodenum 20 when the circumferential groove 47 hassubstantially the same axial position as the papilla of Vater 30. Thepressing of the outer surface 35 against the inner surface 27 providesresistance to axial displacement of the tubular structure 32 relative tothe duodenum 20.

The anti-obesity stent 12 includes a side tube 52 which is connected tothe outer surface 35. The side tube 52 has one end which is connected tothe outer surface 35 and one or more perforations 53 adjacent thereto.The side tube 52 has an opposite end which may be inserted through thepapilla of Vater 30. The papilla of Vater 30 is part of the duodenum 20and supplies the digestive fluids 31 thereto. The digestive fluids 31which are supplied through the papilla of Vater 30 are conveyed throughthe side tube 52 in a direction which is toward the outer surface 35.When the digestive fluids 31 approach the outer surface 35, thedigestive fluids exit the side tube 52 through the perforations 53 andflow into the axial groove 55. Additionally, the insertion of the sidetube 52 into the papilla of Vater 30 anchors the side tube therein. Thisanchoring, in combination with the connection of the side tube 52 to theouter surface 35, substantially fixes the position of the tubularstructure 32 within the duodenum 20 by preventing rotational and axialmigration of the tubular structure relative to the duodenum.

The digestive fluids 31 which collect in the axial groove 55 flow towardthe distal end 42 of the tubular structure 32. Upon reaching the distalend 42, the digestive fluids 31 flow into the duodenum 20. Substantiallyall of the digestive fluids 31 which flow into the duodenum 20 from theaxial groove 55 enter and remain in a portion of the duodenum which hasa distal position relative to the distal end 42. Consequently,substantially all of the digestive fluids 31 are partially or completelyprevented from entering the interior region of the tubular structure 32.As a result, mixing of the chyme 26 and digestive fluids 31 when thechyme is within the tubular structure 32 is partially or completelyprevented.

In an alternative embodiment of the anti-obesity stent 12, the side tube52 may be secured to a region of the outer surface 35 which is proximalto the distal end 42. Such an embodiment of the side tube 52 extendsaxially in the distal direction to the distal end 42. The side tube 52is anchored to the outer surface 35. Consequently, the digestive fluids31 in the side tube 52 exit therefrom adjacent to the distal end 42.This embodiment of the side tube 52 may include one or more perforations53 to provide corresponding additional or alternative ports for thedigestive fluids 31 to exit the side tube. The digestive fluids 31 whichexit the side tube 52 through the perforations 53 may enter the axialgrooves 55 and flow therein to the distal end 42. Also, the digestivefluids 31 may enter the axial grooves 55 upon exiting the distal end ofan embodiment of the side tube 52 which terminates at a location whichis proximal to the distal end 42. Further, an embodiment of the sidetube 52 which extends to the distal end 42 and does not includeperforations 53 may make unnecessary the axial grooves 55.

In a further alternative embodiment of the anti-obesity stent 12, theside tube 52 may extend through the outer surface 35, and through thewall of the tubular structure 32 between the outer surface and innersurface 37 for attachment to a region of the inner surface 37 which isproximal to the distal end 42. Such an embodiment of the side tube 52extends axially in the distal direction to the distal end 42. The sidetube 52 is anchored to the inner surface 37. Consequently, the digestivefluids 31 in the side tube 52 exit therefrom adjacent to the distal end42. This embodiment of the side tube 52 may include one or moreperforations 53 which would typically be located adjacent to the distalend 42 to provide corresponding additional or alternative ports for thedigestive fluids 31 to exit the side tube. The digestive fluids 31 whichexit the side tube 52 through the perforations 53 enter the interior ofthe tubular structure 32 and flow therein to the distal end 42.

In a further alternative embodiment of the anti-obesity stent 12, theside tube 52 may extend through the outer surface 35, and be embedded orburied in the wall of the tubular structure 32 between the outer surfaceand inner surface 37. This embedding or burying is in an axial portionof the tubular structure 32 which is proximal to the distal end 42. Suchan embodiment of the side tube 52 extends axially in the distaldirection to the distal end 42. Consequently, the digestive fluids 31 inthe side tube 52 exit therefrom adjacent to the distal end 42. Thisembodiment of the side tube 52 may include one or more perforations 53which communicate with corresponding apertures in the outer or innersurfaces 35, 37 or both to provide corresponding additional oralternative ports for the digestive fluids 31 to exit the side tube. Thedigestive fluids 31 which exit the side tube 52 through the perforations53 and outer surface 35 may enter the axial grooves 55 and flow thereinto the distal end 42. Also, the digestive fluids 31 may enter the axialgrooves 55 upon exiting the distal end of an embodiment of the side tube52 which terminates at a location which is proximal to the distal end 42and communicates with a port in the outer surface 35. Further, anembodiment of the side tube 52 which extends to the distal end 42 anddoes not include perforations 53 may make unnecessary the axial grooves55. Also, an embodiment of the side tube 52 which has one or moreperforations 53 in communication with corresponding apertures on theinner surface 37 would typically provide for the perforations andapertures to be located adjacent to the distal end 42. The digestivefluids 31 which exit the side tube 52 through the perforations 53 andapertures on the inner surface 37 enter the interior of the tubularstructure 32 and flow therein to the distal end 42.

An embodiment of the anti-obesity stent 12 is possible which does notinclude the side tube 52. Location of this embodiment of theanti-obesity stent 12 within the duodenum 20 provides for the digestivefluids 31, which flow through the papilla of Vater 30 into the interiorof the duodenum 20 to collect in the circumferential groove 47. Thedigestive fluids 31 which collect in the circumferential groove 47 ofthis embodiment flow into and through the axial groove 55 toward thedistal end 42 of the tubular structure 32.

An alternative embodiment of the transport structure 45 includes aconduit which is integral with the tubular structure 32 such that theconduit is between the outer and inner surfaces 35, 37. The digestivefluids 31 in the transport structure 45 are conveyed through the conduitto the distal end 42.

An alternative embodiment of the anti-obesity stent 12 a is shown inFIG. 4. Parts illustrated in FIG. 4 which correspond to partsillustrated in FIGS. 1 to 3 have, in FIG. 4, the same reference numeralas in FIGS. 1 to 3 with the addition of the suffix “a”. In thisalternative embodiment, the transport structure 45 a includes aplurality of axial grooves 55 a. The axial grooves 55 a providecorresponding conduits for the digestive fluids 31 to be conveyed to thedistal end 42 a.

An alternative embodiment of the anti-obesity stent 12 b is shown inFIG. 5. Parts illustrated in FIG. 5 which correspond to partsillustrated in FIGS. 1 to 3 have, in FIG. 5, the same reference numeralas in FIGS. 1 to 3 with the addition of the suffix “b”. In thisalternative embodiment, the transport structure 45 b includes a meshstructure 57. The mesh structure 57 is tubular and has a diameter whichis larger than a diameter of the transverse groove 47 b.

The mesh structure 57 has an annular cross section as a result of thetubular structure 32 b having an annular cross section. Alternativeembodiments of the mesh structure 57 are possible which have non-annularcross sections.

The mesh structure 57 is attached to the tubular structure 32 b incoaxial relation therewith such that the mesh structure covers thecircumferential groove 47 b to provide a transverse or radial clearancebetween the inner surface 27 of the duodenum 20 and the circumferentialgroove. The mesh structure 57 prevents the inner surface 27 of theduodenum 20 from extending into the circumferential groove 47 b. Also,the mesh structure 57 prevents the inner surface 27 of the duodenum 20from contacting the surface of the tubular structure 32 b which iswithin the circumferential groove 47 b. Prevention of such contact bythe inner surface 27 provides for the passage of the digestive fluids 31through the papilla of Vater 30 to be unobstructed by the tubularstructure 32 b. Contact of the inner surface 27 with the tubularstructure 32 b may obstruct passage and flow of the digestive fluids 31through the papilla of Vater 30.

The mesh structure 57 shown in FIG. 5 has substantially the samediameter as the diameter of the outer surface 35 b of the tubularstructure 32 b such that the mesh structure is substantially flush withthe outer surface 35 b. In alternative embodiments, it is possible forthe diameter of the mesh structure 57 to be smaller than the diameter ofthe outer surface 35 b provided that the diameter of the mesh structure57 is larger than the minimum diameter of the transverse groove 47 b.

The side tube 52 b may be anchored to the tubular structure 32 b invarious configurations which correspond to the anchoring of the sidetube 52 to the tubular structure 32. Alternatively, the side tube 52 bmay be anchored to the mesh structure 57.

The anti-obesity stent 12 b includes an alternative embodiment of thetransport structure 45 b. The transport structure 52 b includes a venttube 65 which is attached to the inner surface 37 b of the tubularstructure 32 b. The vent tube 65 communicates with the circumferentialgroove 47 b such that the digestive fluids 31 therein are conveyedthrough the vent tube to the distal end 42 b.

A further alternative embodiment of the anti-obesity stent 12 c is shownin FIG. 6. Parts illustrated in FIG. 6 which correspond to partsillustrated in FIGS. 1 to 3 have, in FIG. 6, the same reference numeralas in FIGS. 1 to 3 with the addition of the suffix “c”. The tubularstructure 32 c has proximal and distal portions 60, 62. The proximalportion 60 has an outer diameter which is larger than the outer diameterof the distal portion 62. The proximal portion 60 has an axial positionwhich is proximal relative to the papilla of Vater 30 when the tubularstructure 32 c is within the duodenum 20.

The proximal and distal portions 60, 62 have respective annular crosssections. Alternative embodiments of the proximal and distal portions60, 62 are possible which have non-annular cross sections.

The transport structure 45 c includes a mesh structure 67 which istubular and has an annular cross section. The diameter of the meshstructure 67 is larger than the diameter of the outer surface 35 c ofthe distal portion 62. The mesh structure 67 is attached to the proximalportion 60 in coaxial relation with the distal portion 62. The meshstructure 67 extends between the proximal portion 60 and distal end 42 csuch that the mesh structure 67 provides a transverse or radialclearance between the inner surface 27 of the duodenum 20 and the outersurface 35 c of the distal portion 62. The transverse or radialclearance provides for the passage of the digestive fluids 31 throughthe papilla of Vater 30 to be unobstructed by the tubular structure 32c. The diameter of the mesh structure 67 is substantially the same asthe outer diameter of the proximal portion 60 such that the meshstructure is substantially flush with the outer surface 35 c of theproximal portion 60.

The side tube 52 c may be anchored to the tubular structure 32 c invarious configurations which correspond to the anchoring of the sidetube 52 to the tubular structure 32. Alternatively, the side tube 52 cmay be anchored to the mesh structure 67.

An alternative embodiment of the anti-obesity stent 12 d is shown inFIG. 7. Parts illustrated in FIG. 7 which correspond to partsillustrated in FIGS. 1 to 3 have, in FIG. 7, the same reference numeralas in FIGS. 1 to 3 with the addition of the suffix “d”. The transportstructure 45 d includes a wick material 70 which is attached to theouter surface 35 d of the tubular structure 32 d. The wick material 70has a structure which may be a mesh or sponge. The wick material 70 hasan annular cross section and extends to the distal end 42 d. The wickmaterial 70 is formed of polymeric fibers which may be hollow.Alternatively, the wick material 70 may possibly be formed of PTFE. Thewick material 70 is in direct contact with the papilla of Vater 30 suchthat the digestive fluids 31 exiting therefrom are absorbed by the wickmaterial and conveyed through the wick material to the distal end 42 d.In alternative embodiments, the digestive fluids 31 in thecircumferential grooves 47, 47 b may be absorbed by the wick material 70and conveyed through the wick material to the distal ends 42, 42 b.

The side tube 52 d may be anchored to the tubular structure 32 d invarious configurations which correspond to the anchoring of the sidetube 52 to the tubular structure 32. When connected to the tubularstructure 32 d, the side tube 52 d may have an axial position whichprovides for the side tube to be in direct contact with the wickmaterial 70 or, alternatively, for the side tube to have a proximalposition relative to the wick material which is axially separated fromthe wick material.

An alternative embodiment of the anti-obesity stent 12 d is shown inFIG. 8. Parts illustrated in FIG. 8 which correspond to partsillustrated in FIGS. 1 to 3 have, in FIG. 8, the same reference numeralas in FIGS. 1 to 3 with the addition of suffix “e”. The transportstructure 45 e includes a groove 72 which has rotational andlongitudinal orientations which are offset relative to the tubularstructure 32 e. These offset rotational and longitudinal orientationsprovide for the groove 72 to be helical in a tubular structure 32 ewhich has an annular cross section, as shown in FIG. 8. The helicalgroove 72 has a longitudinal axis which substantially coincides with thelongitudinal axis of the tubular structure 32 e. The helical groove 72provides a conduit for the digestive fluids 31 to be conveyed to thedistal end 42 e. This results from locating the anti-obesity stent 12 ewithin the duodenum 20 such that a section of the helical groove,typically one near the proximal end 40 e, has the same axial position asthe papilla of Vater 30. Consequently, the digestive fluids 31 whichflow through the papilla of Vater 30 into the interior of the duodenum20 land in the helical groove 72. The digestive fluids 31 in the helicalgroove 72 are displaced toward the distal end 42 e by digestive fluidswhich subsequently flow into the helical groove from the papilla ofVater 30. The digestive fluids 31 remain in the helical groove 72 duringthis displacement thereof in the distal direction such that thedigestive fluids flow around the outer surface 35 e in the direction ofthe helical groove.

The flow of the digestive fluids 31 through the helical groove 72provides for an increase in the exposure and contact of the digestivefluids 31 with the inner surface 27 of the duodenum 20. This contactbetween the digestive fluids 31 and the inner surface 27 is furtherfacilitated by providing the outer surface 35 e with a diameter which issufficiently large to limit the transverse or radial clearance betweenthe outer surface 35 e and the inner surface 27 of the duodenum.Increasing the contact between the digestive fluids 31 and inner surface27 contributes to absorption of the digestive fluids by the innersurface 27 of the duodenum 20. Such absorption of the digestive fluids31 reduces the availability thereof to mix with the chyme 26.

An alternative embodiment of the anti-obesity stent 12 f is shown inFIG. 9. Parts illustrated in FIG. 9 which correspond to partsillustrated in FIGS. 1 to 3 have, in FIG. 9, the same reference numeralas in FIGS. 1 to 3 with the addition of the suffix “f”. In thisalternative embodiment, the tubular structure 32 f is sized to fitwithin the duodenum 20 in substantially coaxial relation therewith. Theouter surface 35 f has a cross section the shape of which issubstantially the same as the shape of the cross section of the innersurface 27 of the duodenum 20. The diameter of the outer surface 35 f ofthe tubular structure 32 f is sufficiently large to limit the formationof a radial clearance between the outer surface 35 f and inner surface27 when the tubular structure 32 f is located within the duodenum 20.The diameter of the outer surface 35 f of the tubular structure 32 f maybe sufficiently large such that the outer surface 35 f engages the innersurface 27 to substantially prevent the formation of a radial clearancebetween the outer surface 35 f and inner surface 27 when the tubularstructure 32 f is located within the duodenum 20. The tubular structure32 f is impervious or semi-permeable to digestive substances and chyme26 within the duodenum 20.

The retainer structure 50 f, which is connected to the outer surface 35f of the tubular structure 32 f, secures the tubular structure 32 fwithin the duodenum 20 such that the proximal end 40 f is adjacent toand distal of the papilla of Vater 30. The distal position of theproximal end 40 f relative to the papilla of Vater 30 does not preventthe chyme 26 from mixing with the digestive fluids 31 which flow throughthe papilla of Vater 30 into the interior of the duodenum 20. The chyme26 and digestive fluids 31 which have an axial position which isproximal relative to the proximal end 40 f flow into the interior of thetubular structure 32 f through the proximal end 40 f. The chyme 26 anddigestive fluids 31 continue to flow through the interior of the tubularstructure 32 f and exit the tubular structure through the distal end 42f.

The limiting of the formation of a radial clearance between the outersurface 35 f of the tubular structure 32 f and the inner surface 27 ofthe duodenum 20 limits the flow of the chyme 26 and digestive fluids 31between the outer surface 35 f and the inner surface 27. Consequently,absorption of the nutrients, fats and other substances in the chyme 26and digestive fluids 31 by the inner surface 27 of the duodenum 20 islimited in the axial portion of the duodenum 20 in which the tubularstructure 32 f is located. As a result, absorption of the nutrients,fats and other substances in the chyme 26 by the duodenum 20 is reduced.

An alternative embodiment of the anti-obesity stent 12 g is shown inFIG. 10. Parts illustrated in FIG. 10 which correspond to partsillustrated in FIGS. 1 to 3 have, in FIG. 10, the same reference numeralas in FIGS. 1 to 3 with the addition of the suffix “g”. The retainerstructure 50 g includes a proximal portion 68 of the tubular structure32 g which is axial and contains the proximal end 40 g, as shown in FIG.10. The proximal portion 68 has an axial position which is proximalrelative to the transport structure 45 g. The proximal portion 68 isseparated axially from the transport structure 45 g a sufficientdistance such that the proximal portion 68 extends through the pylorus25 when the transport structure 45 g is positioned to receive thedigestive fluids 31 from the papilla of Vater 30. The extension of theproximal portion 68 through the pylorus 25 provides for the chyme 26 toenter the tubular structure 32 g in the pyloric portion 22 of thestomach 17. Consequently, the chyme 26 is within the tubular structure32 g when the chyme enters the duodenum 20. This obstructs the chyme 26from being absorbed by the inner surface 27 or mixing with the digestivefluids 31 in the duodenum 20 which are upstream of the distal end 42 g.

The proximal portion 68 is outwardly flared such that the proximal end40 g and an adjoining part of the proximal portion 68 which extendsthrough the pylorus 25 has an outer diameter which is larger than anouter diameter of an intermediate portion of the tubular structure 32 g.The outward flaring of the proximal portion 68 provides resistance toaxial displacement of the tubular structure 32 g in a distal directionrelative to the duodenum 20. The proximal portion 68 and intermediateportion of the tubular structure 32 g have annular cross sections as aresult of the tubular structure 32 g having an annular cross section.The retainer structure 50 g may be incorporated into alternativeembodiments of the anti-obesity stent, such as the anti-obesity stents12, 12 a, 12 b, 12 c, 12 d, 12 e.

The proximal portion 68 of the tubular structure 32 g has an outerdiameter which is sufficiently large to press against the inner surfaceof the pylorus 25 such that resistance to axial displacement of thetubular structure 32 g relative to the duodenum 20 is provided. Theproximal portion 68 has an annular cross section. The retainer structure50 g may further include a circumferential groove formed on the outersurface of the proximal portion 68 which extends through the pylorus 25.This circumferential groove is located axially relative to the proximalportion 68 such that the inner surface of the pylorus 25 extends intothe circumferential groove such that resistance to axial displacement ofthe tubular structure 32 g relative to the duodenum 20 is provided. Thecircumferential groove is transverse relative to the proximal portion68, and may be circular.

An alternative embodiment of the anti-obesity stent 12 h is shown inFIG. 11. Parts illustrated in FIG. 11 which correspond to partsillustrated in FIGS. 1 to 3 have, in FIG. 11, the same reference numeralas in FIGS. 1 to 3 with the addition of the suffix “h”. In thisalternative embodiment, the retainer structure 50 h includes a proximalanchor 75 which is tubular and has an inner surface which is connectedto the outer surface 35 h of the tubular structure 32 h. The proximalanchor 75 is located adjacent to the proximal end 40 h. The retainerstructure 50 h further includes a distal anchor 77 which is tubular andhas an inner surface which is connected to the outer surface 35 h. Thedistal anchor 77 is located adjacent to the distal end 42 h.

The proximal and distal anchors 75, 77 are transversely expandable toouter diameters which are sufficiently large such that correspondingouter surfaces 80, 82 of the proximal and distal anchors engage theinner surface 27 of the duodenum 20. This engagement substantiallyprevents the formation of a radial clearance between the outer surfaces80, 82 and the inner surface 27 when the tubular structure 32 h islocated within the duodenum 20 such that the papilla of Vater 30 isaxially positioned between the proximal and distal anchors 75, 77. Theaxial positioning of proximal and distal anchors 75, 77 relative to thepapilla of Vater 30 allows the digestive fluids 31 which flow throughthe papilla of Vater into the duodenum 20 to become contained betweenthe tubular structure 32 h and the inner surface 27. The distal anchor77 or a distal portion of the tubular structure 32 h or both arepermeable to the digestive fluids 31 contained between the tubularstructure 32 h and the inner surface 27 of the duodenum 20.

An alternative embodiment of the anti-obesity stent 12 i is shown inFIG. 12. Parts illustrated in FIG. 12 which correspond to partsillustrated in FIGS. 1 to 3 have, in FIG. 12, the same reference numeralas in FIGS. 1 to 3 with the addition of the suffix “i”. In thisalternative embodiment, the transport structure 45 i includes anelongate support member 85 which is secured to the outer surface 35 i ofthe tubular structure 32 i. The support member 85 has rotational andlongitudinal orientations which are offset relative to the tubularstructure 32 i. These offset rotational and longitudinal orientationsprovide for the support member 85 to be helical in a tubular structure32 i which has an annular cross section, as shown in FIG. 12. Thesupport member 85 has a longitudinal axis which substantially coincideswith the longitudinal axis of the tubular structure 32 i. The supportmember 85 contacts the inner surface 27 of the duodenum 20 and providesa transverse or radial clearance between the inner surface 27 and theouter surface 35 i of the tubular structure 32 i. The transverse orradial clearance provides for the separation of the tubular structure 32i from the papilla of Vater 30 to facilitate the flow of the digestivefluids 31 out of the papilla of Vater 30.

The support member 85 includes a tubular structure 87 having proximaland distal ends 90, 92 which are open. The digestive fluids 31 may flowthrough the proximal end 90 into the lumen of the tubular structure 87.The digestive fluids 31 are carried through the lumen to the distal end90.

The support member 85 has perforations 95 in the tubular structure 87.The perforations 95 provide for the digestive fluids 31 to flow into thelumen of the tubular structure 87. The digestive fluids 31 which flowinto the lumen are carried therein in the distal direction and may exittherefrom through the distal end 92.

An alternative embodiment of the support member 85 is possible in whichthe proximal end 90 is closed such that the perforations 95 provide forthe entry of the digestive fluids 31 into the lumen of the tubularstructure 87. A further alternative embodiment of the support member 85is possible which does not have the perforations 95 such that theopening in the proximal end 90 provides for the entry of the digestivefluids 31 into the lumen of the tubular structure 87. A furtheralternative embodiment of the support member 85 is possible in which thetubular structure 87 does not have a lumen such that the digestivefluids 31 flow in the transverse or radial clearance between the innersurface 27 of the duodenum 20 and the outer surface 35 i of the tubularstructure 32 i toward the distal end 42 i.

The securing of the support member 85 to the outer surface 35 i fixesthe support member thereto. The contact between the support member 85and inner surface 27 provides resistance to displacement of the supportmember 85 relative to the inner surface 27. Consequently, the supportmember 85 provides the retainer structure 50 i.

In a further alternative embodiment, the support member 85 may includeat least three longitudinal support members which are secured to theouter surface 35 i as an alternative to the helical support member shownin FIG. 12. The longitudinal support members have longitudinalorientations relative to the tubular structure 32 i. The longitudinalsupport members are spaced equidistant from one anothercircumferentially relative to the outer surface 35 i. The longitudinalsupport members provide a transverse or radial clearance between theinner and outer surfaces 27, 35 i.

The longitudinal support members each include a tubular structure havingproximal and distal ends which are open. The digestive fluids 31 mayflow through the proximal ends into the lumen of the tubular structuresof the longitudinal support members. The digestive fluids 31 are carriedthrough the lumens to the distal ends of the longitudinal supportmembers.

The longitudinal support members have perforations in the correspondingtubular structures thereof. The perforations provide for the digestivefluids 31 to flow into the lumens of the tubular structures. Thedigestive fluids 31 which flow into the lumens are carried therein inthe distal direction and may exit therefrom through the distal ends.

An alternative embodiment of the longitudinal support members ispossible in which the corresponding proximal ends are closed such thatthe perforations provide for the entry of the digestive fluids 31 intothe lumens of the tubular structures. A further alternative embodimentof the longitudinal support members is possible which does not have theperforations such that the open proximal ends provide for the entry ofthe digestive fluids 31 into the lumens of the tubular structures. Afurther alternative embodiment of the longitudinal support members ispossible in which the tubular structures do not have correspondinglumens such that the digestive fluids 31 flow in the transverse orradial clearance between the inner surface 27 of the duodenum 20 and theouter surface of the tubular structure toward the distal end thereof.

The securing of the longitudinal support members to the outer surface ofthe tubular structure fixes the support members thereto. The contactbetween the longitudinal support members and inner surface 27 providesresistance to displacement of the support members relative to the innersurface 27. Consequently, the longitudinal support members provide theretainer structure.

Alternative embodiments of the anti-obesity stent 12, 12 a, 12 b, 12 c,12 d, 12 e, 12 f, 12 g, 12 h, 12 i have respective retainer structures50, 50 a, 50 b, 50 c, 50 d, 50 e, 50 f, 50 g, 50 h which include acircumferential groove formed on the outer surface 35, 35 a, 35 b, 35 c,35 d, 35 e, 35 f, 35 g, 35 h such that the inner surface 27 of theduodenum 20 extends into the circumferential groove to provideresistance to axial displacement of the tubular structure 32, 32 a, 32b, 32 c, 32 d, 32 e, 32 f, 32 g, 32 h relative to the duodenum 20. Sucha circumferential groove is transverse relative to the tubular structure32, 32 a, 32 b, 32 c, 32 d, 32 e, 32 f, 32 g, 32 h and may be circular.

Further alternative embodiments of the anti-obesity stent 12, 12 a, 12b, 12 c, 12 d, 12 e, 12 f, 12 g, 12 h have respective retainerstructures 50, 50 a, 50 b, 50 c, 50 d, 50 e, 50 f, 50 g, 50 h whichinclude a protuberance extending from the outer surface 35, 35 a, 35 b,35 c, 35 d, 35 e, 35 f, 35 g, 35 h of the tubular structure 32, 32 a, 32b, 32 c, 32 d, 32 e, 32 f, 32 g, 32 h. The protuberance has an outersurface and a radial dimension such that the outer surface of theprotuberance engages the inner surface 27 of the duodenum 20 when thetubular structure 32, 32 a, 32 b, 32 c, 32 d, 32 e, 32 f, 32 g, 32 h, 32i is located within the duodenum 20 and the axial position of thetransport structure 45, 45 a 45 b, 45 c, 45 d, 45 e, 45 f, 45 g, 45 h,45 i is positioned to receive the digestive fluids 31 from the papillaof Vater 30. The engagement of the protuberance with the inner surface27 of the duodenum 20 provides resistance to axial displacement of thetubular structure 32, 32 a, 32 b, 32 c, 32 d, 32 e, 32 f, 32 g, 32 h, 32i relative to the duodenum 20. The protuberance may include hooks andpins which have a distal end which is pointed and may include one ormore barbs. The protuberance may engage the inner surface 27 to providethe resistance to axial displacement of the tubular structure 32, 32 a,32 b, 32 c, 32 d, 32 e, 32 f, 32 g, 32 h, 32 i for the tubularstructures having outer surfaces 35, 35 a, 35 b, 35 c, 35 d, 35 e, 35 f,35 g, 35 h, 35 i with various diameters. Such outer surfaces 35, 35 a,35 b, 35 c, 35 d, 35 e, 35 f, 35 g, 35 h, 35 i may have a diameter whichis smaller than the diameter of the inner surface 27 or, alternatively,may have a diameter which is larger than the diameter of the innersurface 27. The tubular structures 32, 32 a, 32 b, 32 c, 32 d, 32 e, 32f, 32 g, 32 h, 32 i may have an annular cross section such that theouter surfaces 35, 35 a, 35 b, 35 c, 35 d, 35 e, 35 f, 35 g, 35 h, 35 iare circular.

Further alternative embodiments of the anti-obesity stents 12, 12 a, 12b, 12 c, 12 d, 12 e, 12 f, 12 g, 12 h have respective retainerstructures 50, 50 a, 50 b, 50 c, 50 d, 50 e, 50 f, 50 g, 50 h whichinclude one or more sections of the outer surface 35, 35 a, 35 b, 35 c,35 d, 35 e, 35 f, 35 g, 35 h being roughened or knurled. Such outersurfaces 35, 35 a, 35 b, 35 c, 35 d, 35 e, 35 f, 35 g, 35 h have adiameter which is substantially the same as or larger than the diameterof the inner surface 27. The tubular structures 32, 32 a, 32 b, 32 c, 32d, 32 e, 32 f, 32 g, 32 h may have an annular cross section such thatthe outer surfaces 35, 35 a, 35 b, 35 c, 35 d, 35 e, 35 f, 35 g, 35 hare circular.

Further alternative embodiments of the anti-obesity stent 12, 12 a, 12b, 12 c, 12 d, 12 e, 12 f, 12 g, 12 h have respective retainerstructures 50, 50 a, 50 b, 50 c, 50 d, 50 e, 50 f, 50 g, 50 h whichinclude a semi-rigid band secured to the tubular structure 32, 32 a, 32b, 32 c, 32 d, 32 e, 32 f, 32 g, 32 h. The semi-rigid band is arcuate orcircular, and has a transverse orientation relative to the tubularstructure 32, 32 a, 32 b, 32 c, 32 d, 32 e, 32 f, 32 g, 32 h. Thesemi-rigid band is transversely expandable to one or more outerdiameters which are sufficiently large to anchor the tubular structure32, 32 a, 32 b, 32 c, 32 d, 32 e, 32 f, 32 g, 32 h to the inner surface27 of the duodenum 20. The semi-rigid band may have a ratchetingmechanism which provides for the transverse expansion of the band. Thesemi-rigid band may include polymeric material or metal.

Further alternative embodiments of the anti-obesity stent 12, 12 a, 12b, 12 c, 12 d, 12 e, 12 f, 12 g, 12 h have respective retainerstructures 50, 50 a, 50 b, 50 c, 50 d, 50 e, 50 f, 50 g, 50 h whichinclude a collapsible ring structure which is secured to the tubularstructure 32, 32 a, 32 b, 32 c, 32 d, 32 e, 32 f, 32 g, 32 h. Such acollapsible ring structure may improve the opening and retention of thetubular structure 32, 32 a, 32 b, 32 c, 32 d, 32 e, 32 f, 32 g, 32 hwithin the duodenum 20.

Further alternative embodiments of the anti-obesity stents 12, 12 a, 12b, 12 c, 12 d, 12 e, 12 f, 12 g, 12 h, 12 i have respective retainerstructures 50, 50 a, 50 b, 50 c, 50 d, 50 e, 50 f, 50 g, 50 h, 50 iwhich include one or more elongate anchor members which are secured tothe tubular structure 32, 32 a, 32 b, 32 c, 32 d, 32 e, 32 f, 32 g, 32h, 32 i. Each anchor member is arcuate, and has a transverse orientationrelative to the tubular structure 32, 32 a, 32 b, 32 c, 32 d, 32 e, 32f, 32 g, 32 h, 32 i. The arcuate extent of the anchor members may be 300degrees. The anchor members extend radially outward from the outersurfaces 35, 35 a, 35 b, 35 c, 35 d, 35 e, 35 f, 35 g, 35 h, 35 i asufficient distance to anchor the tubular structure 32, 32 a, 32 b, 32c, 32 d, 32 e, 32 f, 32 g, 32 h, 32 i to the inner surface 27 of theduodenum 20. The arcuate configuration of the one or more anchor membersprovides corresponding circumferential gaps between the ends of eacharcuate member. The circumferential gaps provide increased radialclearances in the locations thereof in the region between the outersurfaces 35, 35 a, 35 b, 35 c, 35 d, 35 e, 35 f, 35 g, 35 h, 35 i andthe inner surface 27 which facilitates the axial flow of the digestivefluids 31 through the region.

Further alternative embodiments of the anti-obesity stent 12, 12 a, 12b, 12 c, 12 d, 12 e, 12 f, 12 g, 12 h have respective retainerstructures 50, 50 a, 50 b, 50 c, 50 d, 50 e, 50 f, 50 g, 50 h whichinclude sutures. Such sutures anchor the outer surface 35, 35 a, 35 b,35 c, 35 d, 35 e, 35 f, 35 g, 35 h of the tubular structure 32, 32 a, 32b, 32 c, 32 d, 32 e, 32 f, 32 g, 32 h to the inner surface 27 of theduodenum 20 and, in some embodiments, to the stomach 17. The suturesprevent axial and rotational displacement of the anti-obesity stents 12,12 a, 12 b, 12 c, 12 d, 12 e, 12 f, 12 g, 12 h relative to the duodenum20 and stomach 17.

Further alternative embodiments of the anti-obesity stents 12, 12 a, 12b, 12 c, 12 d, 12 e, 12 f, 12 g, 12 h have respective retainerstructures 50, 50 a, 50 b, 50 c, 50 d, 50 e, 50 f, 50 g, 50 h whichinclude an adhesive material which bonds the outer surface 35, 35 a, 35b, 35 c, 35 d, 35 e, 35 f, 35 g, 35 h and inner surface 27 to oneanother. Such outer surfaces 35, 35 a, 35 b, 35 c, 35 d, 35 e, 35 f, 35g, 35 h have a diameter which is substantially the same as or largerthan the diameter of the inner surface 27. The tubular structures 32, 32a, 32 b, 32 c, 32 d, 32 e, 32 f, 32 g, 32 h may have an annular crosssection such that the outer surfaces 35, 35 a, 35 b, 35 c, 35 d, 35 e,35 f, 35 g, 35 h are circular. A further alternative embodiment of theanti-obesity stent 12 i has a retainer structure 50 i which includes anadhesive material which bonds the outer surface of the support member 85and inner surface 27 to one another.

Further alternative embodiments of the anti-obesity stents 12, 12 a, 12b, 12 c, 12 d, 12 e, 12 f, 12 g, 12 h have respective retainerstructures 50, 50 a, 50 b, 50 c, 50 d, 50 e, 50 f, 50 g, 50 h whichinduce cells, such as are present on the inner surface 27 of theduodenum 20, to grow into the outer surfaces 35, 35 a, 35 b, 35 c, 35 d,35 e, 35 f, 35 g, 35 h of the tubular structures 32, 32 a, 32 b, 32 c,32 d, 32 e, 32 f, 32 g, 32 h. A further alternative embodiment of theanti-obesity stent 12 i has a retainer structure 50 i which inducescells, such as are present on the inner surface 27 of the duodenum 20,to grow into the outer surface of the support member 85.

Further alternative embodiments of the anti-obesity stents 12, 12 a, 12b, 12 c, 12 d, 12 e, 12 f, 12 g, 12 h have respective retainerstructures 50, 50 a, 50 b, 50 c, 50 d, 50 e, 50 f, 50 g, 50 h whichinclude a balloon or sponge located within the tubular structures 32, 32a, 32 b, 32 c, 32 d, 32 e, 32 f, 32 g, 32 h. Such a balloon and spongeexpands after the tubular structure 32, 32 a, 32 b, 32 c, 32 d, 32 e, 32f, 32 g, 32 h is positioned in the duodenum 20. The expansion of theballoon and sponge results in radial expansion of the tubular structures32, 32 a, 32 b, 32 c, 32 d, 32 e, 32 f, 32 g, 32 h to cause engagementof the outer surfaces 35, 35 a, 35 b, 35 c, 35 d, 35 e, 35 f, 35 g, 35 hwith the inner surface 27 which anchors the tubular structure within theduodenum 20.

Alternative embodiments of the anti-obesity stent 12, 12 a, 12 b, 12 c,12 d, 12 e, 12 f, 12 g, 12 h, 12 i provide for different embodiments ofthe transport structures 45, 45 a, 45 b, 45 c, 45 d, 45 e, 45 f, 45 g,45 h, 45 i to be used in combination with one another such that thedigestive fluids 31 therein are conveyed through the respectivetransport structures to the distal end 42, 42 a, 42 b, 42 c, 42 d, 42 e,42 f, 42 g, 42 h, 42 i. Such combinations of the transport structures45, 45 a, 45 b, 45 c, 45 d, 45 e, 45 f, 45 g, 45 h, 45 i provide for oneof the transport structures to constitute a proximal transport structurewhich is in direct communication with the papilla of Vater 30. Anotherof the transport structures is contiguous with the distal end 42, 42 a,42 b, 42 c, 42 d, 42 e, 42 f, 42 g, 42 h, 42 i. The proximal and distaltransport structures may be directly connected to one another to providea conduit for conveying the digestive fluids 31 from the papilla ofVater 30 to the distal end 42, 42 a, 42 b, 42 c, 42 d, 42 e, 42 f, 42 g,42 h, 42 i. In further alternative embodiments, additional transportstructures may be connected between the proximal and distal transportstructures to provide a conduit for conveying the digestive fluids 31,sequentially through the respective transport structures, from thepapilla of Vater 30 to the distal end 42, 42 a, 42 b, 42 c, 42 d, 42 e,42 f, 42 g, 42 h, 42 i.

An anti-obesity stent, such as the anti-obesity stent 12, 12 a, 12 b, 12c, 12 d, 12 e, 12 f, 12 g, 12 h, 12 i, may be used according to a methodfor inducing weight loss in a patient. The method includes inserting atubular structure of the anti-obesity stent into a duodenum, such as theduodenum 20, in substantially coaxial relation therewith. The tubularstructure has outer and inner surfaces and proximal and distal ends.Embodiments of the tubular structure to which this inserting may beapplied include the tubular structures 32, 32 a, 32 b, 32 c, 32 d, 32 e,32 f, 32 g, 32 h, 32 i. The anti-obesity stent has a transport structureat least a part of which is connected to the outer surface of thetubular structure. The transport structure extends to the distal end.

The method further includes locating the tubular structure within andaxially relative to the duodenum such that the transport structure ispositioned to receive digestive fluids from a papilla of Vater, such asthe papilla of Vater 30, on an inner surface of the duodenum.Embodiments of the transport structure to which this locating may beapplied are the transport structures 45, 45 a, 45 b, 45 c, 45 d, 45 e,45 f, 45 g, 45 h, 45 i. The locating further positions the anti-obesitystent such that the distal end of the tubular structure has a distalposition relative to the papilla of Vater. Embodiments of the distal endof the tubular structure to which this locating may be applied includethe distal ends 42, 42 a, 42 b, 42 c, 42 d, 42 e, 42 f, 42 g, 42 h, 42i.

The method further includes engaging a retainer structure of theanti-obesity stent with the inner surface of the duodenum to secure thetransport structure in the position thereof to receive digestive fluidsfrom the papilla of Vater. Embodiments of the retainer structure towhich this engaging may be applied include the retainer structures 50,50 a, 50 b, 50 c, 50 d, 50 e, 50 f, 50 g, 50 h, 50 i.

The method for inducing weight loss in a patient may provide for the useof an anti-obesity stent in which the transport structure thereof has agroove which is formed on the outer surface. Such anti-obesity stentsare shown in FIGS. 1 to 5, and 8, and include grooves 47, 55 a, 47 b,72. In this embodiment of the method, the locating of the tubularstructure includes positioning the groove such that a section thereofhas circumferential and axial positions which are substantially the sameas the circumferential and axial positions of the papilla of Vaterwithin the duodenum. The engaging of the retainer structure includesengaging the retainer structure with the inner surface of the duodenumto secure the section of the groove in the circumferential and axialpositions thereof which are substantially the same as thecircumferential and axial positions of the papilla of Vater.

The method for inducing weight loss in a patient may provide for the useof an anti-obesity stent in which the transport structure thereof has acircumferential groove which is formed on the outer surface. Such acircumferential groove is continuous, and transverse relative to thetubular structure. Such anti-obesity stents are shown in FIGS. 1 to 3and 5, and include circumferential grooves 47, 47 b. In this embodimentof the method, the locating of the tubular structure includespositioning the circumferential groove such that an axial positionthereof is substantially the same as the axial position of the papillaof Vater when the tubular structure is secured within the duodenum bythe retainer structure. The engaging of the retainer structure includesengaging the retainer structure with the inner surface of the duodenumto secure the circumferential groove in the axial position thereof whichis substantially the same as the axial position of the papilla of Vater.

U.S. Pat. No. 6,740,121 is hereby incorporated by reference herein. Thefollowing U.S. Patent Applications are hereby incorporated by referenceherein:

Title: Anti-Obesity Dual Stent; Inventors: Katie Krueger, WilliamBertolino, Barry Weitzner, and Claude Clerc; Filed on same date aspresent U.S. Patent Application; Attorney Docket No.: 792-40;

Title: Anti-Obesity Diverter Structure; Inventors: Katie Krueger, andHarold W. Martins; Filed on same date as present U.S. PatentApplication; Attorney Docket No.: 792-42; and

Title: Anti-Obesity Flow Controller; Inventor: Barry Weitzner; Filed onsame date as present U.S. Patent Application; Attorney Docket No.:792-43.

While the invention has been described by reference to certain preferredembodiments, it should be understood that numerous changes could be madewithin the spirit and scope of the inventive concept described.Accordingly, it is intended that the invention not be limited to thedisclosed embodiments, but that it have the full scope permitted by thelanguage of the following claims.

1. A stent comprising: a tubular structure having outer and innersurfaces and proximal and distal ends, said tubular structure beingsized to fit within an intestine in substantially coaxial relationtherewith, said tubular structure being impervious or semi-permeable todigestive substances and chyme within the intestine; a transportstructure at least a part of which is coincident with or connected tosaid outer surface, said transport structure extending to said distalend; and at least one retainer structure connected to said tubularstructure, said retainer structure securing said tubular structurewithin the intestine such that said transport structure is positioned toreceive digestive fluids from an inner surface of the intestine, saidtransport structure providing a conduit for the digestive fluids thereinto flow to said distal end.
 2. A stent according to claim 1, wherein theintestine includes a duodenum and a papilla of Vater on the innersurface thereof, said retainer structure securing said tubular structurewithin the duodenum such that said transport structure is positioned toreceive digestive fluids from the papilla of Vater.
 3. A stent accordingto claim 1, wherein said transport structure comprises a groove which isformed on said outer surface.
 4. A stent according to claim 3, whereinsaid groove comprises a circumferential groove, said groove comprisingan axial groove which communicates with said circumferential groove,said axial groove extending between said circumferential groove anddistal end.
 5. A stent according to claim 3, wherein said groovecomprises a circumferential groove, said transport structure comprisinga mesh structure which is attached to said tubular structure such thatsaid mesh structure covers at least a portion of said circumferentialgroove to provide a transverse or radial clearance between the innersurface of the duodenum and said at least a portion of saidcircumferential groove.
 6. A stent according to claim 1, wherein theintestine includes a duodenum and a papilla of Vater on the innersurface thereof, said tubular structure having a proximal portion and adistal portion, said proximal portion having an outer diameter which islarger than an outer diameter of said distal portion, said retainerstructure securing said tubular structure within the duodenum such thatsaid proximal portion has an axial position which is proximal relativeto the papilla of Vater when said tubular structure is located therein,said transport structure comprising a mesh structure which is tubularand has a diameter which is larger than said outer diameter of saiddistal portion, said mesh structure being attached to said proximalportion in coaxial relation with said distal portion, said meshstructure extending between said proximal portion and distal end suchthat said mesh structure provides a transverse or radial clearancebetween the inner surface of the duodenum and said distal portion.
 7. Astent according to claim 1, wherein said transport structure comprises avent tube which is attached to said inner surface of said tubularstructure such that the digestive fluids in said transport structure areconveyed through said vent tube to said distal end.
 8. A stent accordingto claim 1, wherein said transport structure comprises a conduit whichis integral with said tubular structure such that said conduit isbetween said outer and inner surfaces of said tubular structure, thedigestive fluids in said transport structure being conveyed through saidconduit to said distal end.
 9. A stent according to claim 1, whereinsaid transport structure comprises a wick material attached to saidouter surface of said tubular structure, said wick material being indirect contact with the inner surface of the intestine such that thedigestive fluids secreted therefrom are absorbed by said wick materialand conveyed through said wick material to said distal end.
 10. A stentaccording to claim 9, wherein said wick material comprises a mesh orsponge structure.
 11. A stent according to claim 9, wherein said wickmaterial surrounds at least a portion of said tubular structure.
 12. Astent according to claim 3, wherein said groove has rotational andlongitudinal orientations which are offset relative to said tubularstructure.
 13. A stent according to claim 3, wherein said groovecomprises a plurality of axial grooves.
 14. A stent according to claim1, wherein the intestine includes a duodenum and a papilla of Vater onthe inner surface thereof, said stent comprising a side tube which isconnected to said outer surface and in communication with said transportstructure, said side tube being insertable through the papilla of Vatersuch that digestive fluids therein are conveyed through said side tubeinto said transport structure, said side tube resisting axial androtational displacement of said tubular structure relative to theduodenum when said side tube is inserted into the papilla of Vater. 15.A stent comprising: a tubular structure having outer and inner surfacesand proximal and distal ends, said tubular structure being sized to fitwithin a duodenum in substantially coaxial relation therewith, saidouter surface having a cross section the transverse dimension of whichis sufficiently large such that said outer surface of said tubularstructure engages the inner surface of the duodenum to limit a formationof a transverse or radial clearance between said outer surface of saidtubular structure and the inner surface of the duodenum when saidtubular structure is located within the duodenum, said tubular structurebeing impervious or semi-permeable to digestive substances and chymewithin the duodenum; and at least one retainer structure connected tosaid outer surface of said tubular structure, said retainer structuresecuring said tubular structure within the duodenum such that saidproximal end is adjacent to and distal of the papilla of Vater.
 16. Astent according to claim 1, wherein said retainer structure comprises aproximal anchor which is tubular and has an inner surface which isconnected to said outer surface, said proximal anchor being adjacent tosaid proximal end, said retainer structure further comprising a distalanchor which is tubular and has an inner surface which is connected tosaid outer surface, said distal anchor being adjacent to said distalend, said proximal and distal anchors being transversely or radiallyexpandable to outer diameters which are sufficiently large such thatcorresponding outer surfaces of said proximal and distal anchors engagethe inner surface of the intestine to substantially prevent a formationof a transverse or radial clearance between said outer surfaces of saidproximal and distal anchors and the inner surface of the intestine whenthe tubular structure is located therein such that digestive fluidswhich are secreted by the inner surface of the intestine becomecontained between said tubular structure and the inner surface of theintestine, said distal anchor or a distal portion of said tubularstructure being permeable to the digestive fluids contained between saidtubular structure and the inner surface of the intestine.
 17. A stentaccording to claim 16, wherein the intestine includes a duodenum and apapilla of Vater on the inner surface thereof, said tubular structurebeing located within the duodenum such that the papilla of Vater isaxially positioned between said proximal and distal anchors, said axialpositioning of the proximal and distal anchors relative to the papillaof Vater allows digestive fluids which flow through the papilla of Vaterinto the duodenum to become contained between said tubular structure andthe inner surface of the duodenum.
 18. A stent according to claim 1,wherein said retainer structure comprises a diameter of said outersurface of said tubular structure which is sufficiently large to pressagainst the inner surface of the intestine when said transport structureis positioned to receive the digestive fluid from the inner surface ofthe intestine, said retainer structure comprising a circumferentialgroove formed on said outer surface of said tubular structure such thatthe inner surface of the intestine extends into said circumferentialgroove to provide resistance to axial displacement of said tubularstructure relative to the intestine.
 19. A stent according to claim 1,wherein said retainer structure comprises a proximal portion of saidtubular structure which is axial and contains said proximal end, saidproximal portion having an axial position which is proximal relative tosaid transport structure, said proximal portion being separated axiallyfrom said transport structure a sufficient distance such that saidproximal portion extends through a pylorus which leads to the intestinewhen said transport structure is positioned to receive the digestivefluids from the inner surface of the intestine, said proximal portionhaving an outer diameter which is sufficiently large to press against aninner surface of the pylorus, said retainer structure comprising acircumferential groove formed on an outer surface of said proximalportion which extends through the pylorus, said circumferential groovebeing located axially relative to said proximal portion such that theinner surface of the pylorus extends into said circumferential groove toprovide resistance to axial displacement of said tubular structurerelative to the intestine.
 20. A stent according to claim 1, whereinsaid retainer structure comprises a proximal portion of said tubularstructure which is axial and contains said proximal end, said proximalportion having an axial position which is proximal relative to saidtransport structure, said proximal portion being separated axially fromsaid transport structure a sufficient distance such that said proximalportion extends through a pylorus which leads to the intestine when saidtransport structure is positioned to receive digestive fluid from theinner surface of the intestine, said proximal portion being outwardlyflared to provide resistance to axial displacement of said tubularstructure in a distal direction relative to the intestine.
 21. A methodfor inducing weight loss in a patient, said method comprising: insertinga tubular structure of a stent into an intestine in substantiallycoaxial relation therewith, the tubular structure having outer and innersurfaces and proximal and distal ends, the stent having a transportstructure at least a part of which is coincident with or connected tothe outer surface, the transport structure extending to the distal end,the stent having at least one retainer structure connected to the outersurface; locating the tubular structure within and axially relative tothe intestine such that the transport structure is positioned to receivedigestive fluids from an inner surface of the intestine, said locatingfurther positioning the distal end to have a distal position relative tothe receipt of the digestive fluids by the transport structure; andengaging the retainer structure with the inner surface of the intestineto secure the transport structure in the position thereof to receivedigestive fluids from the inner surface of the intestine.
 22. A methodaccording to claim 21, wherein the intestine includes a duodenum and apapilla of Vater on the inner surface thereof, the transport structurehaving a groove which is formed on the outer surface, said locatingcomprising positioning the groove to align with the papilla of Vaterwithin the duodenum, said engaging comprising engaging the retainerstructure with the inner surface of the duodenum to secure the sectionof the groove in the circumferential and axial positions thereof whichare substantially the same as the circumferential and axial positions ofthe papilla of Vater.
 23. A method according to claim 21, wherein theintestine includes a duodenum and a papilla of Vater on the innersurface thereof, the transport structure having a circumferential groovewhich is formed on the outer surface, said locating comprisingpositioning the circumferential groove such that an axial positionthereof is substantially the same as an axial position of the papilla ofVater when the tubular structure is secured within the duodenum by theretainer structure, said engaging comprising engaging the retainerstructure with the inner surface of the duodenum to align thecircumferential groove with the papilla of Vater.